Trigonometry (11th Edition) Clone

Published by Pearson
ISBN 10: 978-0-13-421743-7
ISBN 13: 978-0-13421-743-7

Chapter 5 - Trigonometric Identities - Section 5.3 Sum and Difference Identities for Cosine - 5.3 Exercises - Page 218: 29

Answer

$\tan(-86.9814^\circ)$ is the answer to this exercise.

Work Step by Step

$$\cot176.9814^\circ$$ As cotangent and tangent are cofunctions, $\tan\theta$ is the cofunction needed to find as long as $\theta$ satisfies $$\tan\theta=\cot176.9814^\circ\hspace{1cm}(1)$$ According to Cofunction Identity: $\tan\theta=\cot(90^\circ-\theta)$ Apply this to the equation $(1)$: $$\cot(90^\circ-\theta)=\cot176.9814^\circ$$ $$90^\circ-\theta=176.9814^\circ$$ $$\theta=90^\circ-176.9814^\circ=-86.9814^\circ$$ Hence, $\tan(-86.9814^\circ)$ is the answer to this exercise.
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